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Radiation Protection Phase 1 Lecture 1

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Radiation Protection
Internal/External Hazard
• Internal hazard arises through ingestion
or inhalation of a radiation material – not a
problem in radiology.
Internal/External Hazard
• External hazards
Arise from exposure to external sources.
X-ray sets, emissions from sources etc
Reducing Radiation Dose from
external hazard
TIME
DISTANCE
SHIELDING
PERSONNAL PROTECTION
CLOTHING
Reducing Radiation Dose from
external hazard - TIME
The longer you are exposed to a field
of ionising radiation the higher the
dose you will receive.
Double to time double the dose
Reducing Radiation Dose from
external hazard - DISTANCE
The nearer you stand to an source of
radiation the higher the dose – so stand
away!
Double the distance quarter the
dose
Reducing Radiation Dose from
external hazard - Shielding
Lead shielding can be used to attenuate
X-rays
Room shielding
Screens
Protective clothing
Shielding
пЃ±Need to know type of radiation
– Nuclear Imaging uses g radiation
– Radiochemical Labs use b radiation
пЃ±Plan to use Local Shielding
пЃ±May also need Wall Shielding
Local Shielding
1
пЃ±Vial Shielding
п‚– b emitters - Perspex Vial shields & Storage
п‚– g emitters - Tungsten Vial shields &
lead-lined box for Storage
Vial Shielding b emitters
Vial Shielding g emitters
Local Shielding
2
пЃ±Nuclear Medicine Syringes
п‚– g emitters - Tungsten syringe shields
lead-lined box for Storage
Syringe Shields
g emitters
Local Shielding
3
пЃ±L- Bench Shielding
п‚– g emitters - Lead-lined shields & Lead-glass
п‚– b emitters - Perspex L shields
Lead L- Bench g emitters
PET Dispensing Station
Perspex L Bench b emitters
Local Shielding
4
пЃ±Radioactive Waste Shielding
п‚– g emitters - Sharps bins & Lead-lined
containers
п‚– b emitters - Perspex waste containers, often
lined with polythene bags
Sharps bins & Lead-lined
containers g emitters
Perspex waste containers b
emitters
Wall Shielding
пЃ±Often unnecessary for labs
пЃ±However, same principles employed for
X-ray rooms should be applied to assess
requirements for Radiochemical
Laboratories
Room shielding
Lead glass viewing window
Lead lined plaster board
Reducing Radiation Dose from
Internal hazard
PERSONNAL PROTECTION
CLOTHING
(Training, technique, experience)
Personal Protective Equipment
Fig 3. O versho es
O ften w o rn ro utinely in the
R ad io pharmacy fo r sterility reaso ns.
N ot alw ays o therw ise w o rn ro utinely
to
prevent
the
spread
of
co ntam inatio n, but w id ely used fo r
this purpo se fo llo w ing a sp illag e.
Radiation protection in X-ray
Personal Monitoring
Why monitor non-classified
workers?
• Not likely to receive > 3/10 relevant dose
limit
– (e.g. effective dose > 6 mSv / yr)
• How do you prove this?
• Easiest way is to provide ongoing
monitoring
Thermoluminescent dosemeters
• Measurement range 0. 1 mSv to 5 Sv
• Only issued if risk assessment concludes
they are required
Electronic Dosimeters
• Give an instant reading of dose.
• Measurement range 0.001 mSv to 1 Sv
Other Monitoring
• Extremity
– rings - tlds or electronic
• Eye - tlds
• Internal
– e.g Iodine uptake
– doserate measurements
– swabs
– samples
Contamination
• Spilt or misapplied radionuclides adheres
to or lies on surface of skin, clothing,
equipment or furniture.
• Spills give rise to:
– external radiation
– activity entering body via
• ingestion
• inhalation
• absorption
– leading to internal radiation
Instrumentation for detecting
ionising radiation
• Gas based detectors –
•Geiger- Muller counter,
•GM tube, or
•Geiger counter
• Scintillation detectors •Solid state
•Liquid
Gas filled detectors
Gas
C
Electrodes
V
V = Voltage source
R = High resistance
C = All the capacitance in the detector circuit
R
Scintillation detectors
Scintillation detector
Scintillator
g
Light detector PMT
Conversion of
g to uv or
visible light
pulse
Conversion of light pulse to
an electrical signal
Liquid scintillation - coincidence detection
Scintillator with
radioactive sample
PMT
PMT
Co-incidence
electronics
Liquid scintillation vial
Swab
Contaminant in
intimate contact
with scintillation
medium
Pulse of light
produced with
radiation absorbed
Liquid
scintillant
Mini 900 series EP15 probe
GM gas counter
Mini 900 series E type probe
GM gas counter
Mini 900 series 44A probe
scintillation counter
Solid state
Using the right detector
Beta
Gamma
Tritium (Hydrogen-3)
18.6 keV
Liquid scint
Carbon-14
157 keV
GM tube EP15
Sulphur-35
167 keV
GM tube EP15
Phosphorus-32
1.7 MeV
GM tube EP15 / Scint 44A
Phosphorus-33
2.5 keV
GM tube EP15
Iodine-125
36 keV
Scint 44A / GM tube EP15
Cobalt-60
1.17 MeV &
1.33 MeV
Scint 44A
Caesium-137
Scint 44A
662
Identifying the detector type
• Look at the label on probe
• Scintillation probe heavier
• Scintillation detector higher background rate,
switch it on.
•When in doubt ASK YOUR RPS
Wipe testing
• Use a swab and wipe surface using
tweezers
• Present to appropriate contamination
monitor in low background area
• For low energy Beta use liquid scintillation
counting
Wipe testing
• low level contamination and low energy
Beta. Contamination lifted using
absorbent material and counted in a
gamma counter or liquid scintillation
counter
Radiation spill /incident
Don’t Panic !!!
When dealing with spillage of
radioactive material
• Do not to delay medical care
unnecessarily
• Protect yourselves
• Attend to contaminated persons first
• Prevent the spillage becoming worse
• Prevent additional people from becoming
contaminated
• Clear up and decontaminate the area so it
can be put into use
Urgent medical care
1. If anyone requires urgent medical care,
either by immediate first aid or transfer to
A&E DO THIS FIRST .
– Inform A&E that the casualty is
contaminated. Take any obvious steps to
reduce or eliminate the hazard to the
casualty, to yourselves or anyone attending
the casualty.
– Contact Radiation Protection Service
Protect yourselves
• Pause, take stock and gather information
• Don protective clothing
• If in doubt and there are no casualties
involved, GET HELP – but bear in mind
that you should always try and ensure the
incident is not made worse by your actions
Contaminated persons
• Washing with soap and water. Always try
to localise the contaminated area and just
wash that bit. A whole body shower is
seldom the best approach.
• Remove contaminated clothing
• Washing out any open wound, eyes,
mouth, nose etc.
• If contamination persists contact radiation
protection.
Prevent spillage becoming worse
• Use temporary barriers or close the door.
• Prevent people walking through the
contaminated or potentially contaminated.
• Use an appropriate contamination monitor
to assess the extend of the spill.
• Check personnel for contamination before
they leave the vicinity.
Clear up and decontaminate
• Purpose is to transfer the radioactive material
from the floor or person to the waste store.
• Use absorbent material i.e. paper towels to soak
up the material.
• Dispose in appropriate bin.
• Estimate activity.
• For stubborn areas of contamination use a
normal detergent or decon.
• When clearing up a spill always work from the
outside in.
• Use your contamination monitor!!!
Contamination monitoring
•
•
•
•
•
Know which is the correct monitor to use.
Take care not to contaminate the monitor.
Get down close to the contamination.
Monitor area systematically.
Be thorough .
Other points to note
• Some one should take charge of the
situation.
• Work as a team not as teams of
individuals.
• Have a plan
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